Class 

public class QuoteRollupPFBU {
    
       public QuoteRollupPFBU(){
      List<Quote> quotesToUpdate = new List<Quote>();
      List<QuoteLineItem> quoteLineItemToUpdate;
      quoteLineItemToUpdate = new List<QuoteLineItem>();
    }
        public static void updateQuote(List<SObject> quoteLineItemToUpdate){
            List<Quote> quotesToUpdate = new List<Quote>();
            Set<String> setQuoteProdsToRemove = new  Set<String>();
            List<String> listQuoteProdsToRemove = new List<String>();
            Set<Id> ParentIds = new Set<Id>();
            for(QuoteLineItem qProduct: (List<QuoteLineItem>)quoteLineItemToUpdate){
                System.debug( 'value :' + quoteLineItemToUpdate);
                ParentIds.add(qProduct.QuoteId); 
            }                                            
            Map<Id, Quote> mapQuote = new Map<Id, Quote>([Select Id, ProductBusinessUnits__c, RollupofProductFamilies__c,  (Select Id, QuoteId, ProductFamily__c, Product2Id, LineNumber, BusinessUnit__c from QuoteLineItems Where  (LineNumber != null) ) From Quote Where Id In: ParentIds]); 

           if(Trigger.isInsert || Trigger.isUpdate ){ 
               for(Quote q : mapQuote.values()){
  
                   List<String> quoteLineItemProductFamList = new List<String>();
                   List<String> quoteLineItemBUList = new List<String>();
                   Set<String> qliProdFamSet = new Set<String>();
                   Set<String> qliBUSet = new Set<String>();
                   
                   for(QuoteLineItem qli: q.quotelineitems){
                       if(qli.LineNumber != null  ){
                       qliProdFamSet.add(qli.ProductFamily__c);
                       qliBUSet.add(qli.BusinessUnit__c);   
                       }
                        else if(qli.LineNumber == null ){
                          qliBUSet.remove(qli.BusinessUnit__c);
                          qliProdFamSet.remove(qli.ProductFamily__c);
                           }
                           
                   }
                       
                   
                   quoteLineItemProductFamList.addAll(qliProdFamSet);
                   quoteLineItemProductFamList.sort();
                   String productFamily = string.join(quoteLineItemProductFamList,', ' );
                   
                   quoteLineItemBUList.addAll(qliBUSet);
                   quoteLineItemBUList.sort();
                   String businessUnit = string.join(quoteLineItemBUList,', ' );
                   
                   if(q.RollupofProductFamilies__c != productFamily &&  q.ProductBusinessUnits__c != businessUnit ){
                       q.RollupofProductFamilies__c = productFamily;
                        q.ProductBusinessUnits__c = businessUnit;
                   quotesToUpdate.add(q);
                   }
                                     
               }
              //End of for loop above
               
               if(!quotesToUpdate.isEmpty()){
                   upsert quotesToUpdate;
               }
           }
         
                       }
  
            }




Test Class 

@isTest(SeeAllData = true)
public class QLITest {
    
          @isTest static void RollUpQLI(){
       List<QuoteLineItem> listQLI = new List<QuoteLineItem>();
       List<Quote> quotesToUpdate = new List<Quote>();
       Set<Id> ParentIds = new Set<Id>();
      
      
       //Insert product
       Product2 p = new Product2(Name = 'Test Name', BusinessUnit__c = 'CDS', ProductFamily__c = 'Communication Director');   
       insert p;
       //Insert pricebook
       Pricebook2 standardPricebook = new Pricebook2(Id = Test.getStandardPricebookId(), IsActive = true);
       update standardPricebook;
      // Id pricebookId = Test.getStandardPricebookId();
       
       PricebookEntry pbe1 = new PricebookEntry(Pricebook2id = standardPricebook.Id, Product2id=p.Id, isActive = true, unitPrice=100);
       insert pbe1;
              
        Opportunity o = new Opportunity(Pricebook2id = Test.getStandardPricebookId(), Name = 'Test Opp1', RollupofProductFamilies__c = 'Test', ProductBusinessUnits__c = 'Bed Stat', StageName ='Test Stage', CloseDate = date.today());
        insert o;  
        Quote q = new Quote(OpportunityId = o.Id, Name = 'Test Quote', Pricebook2Id = standardPricebook.Id);   
        insert q;
              
       QuoteLineItem oli = new QuoteLineItem(PricebookEntryid = pbe1.Id, ProductFamily__c = 'Bed Stat', QuoteId = q.Id, Product2Id = p.Id, Quantity = 1, UnitPrice = 1); 
       insert oli;
        listQLI.add(oli);
        upsert listQLI;
        ParentIds.add(oli.QuoteId);
        Map<Id, Quote> mapQuote = new Map<Id, Quote>([Select Id, BusinessUnit__c, ProductBusinessUnits__c, RollupofProductFamilies__c, (Select Id, QuoteId, Product2Id, LineNumber, ProductFamily__c,  BusinessUnit__c from QuoteLineItems ) From Quote Where Id In: ParentIds]);                                                   

        for(Quote quote: mapQuote.values()){
             List<String> qliProdFamList = new List<String>();
             Set<String> qlitProdFamSet = new Set<String>();
             Set<String> qlitBUset = new Set<String>();
             List<String> qliBUList = new List<String>();
              for(QuoteLineItem ql: quote.QuoteLineItems){
                       
                       qlitProdFamSet.add(ql.ProductFamily__c);
                       qlitBUset.add(ql.BusinessUnit__c);

                   }
                   qliProdFamList.addAll(qlitProdFamSet);
                   qliProdFamList.sort();
                   String productFamily = string.join(qliProdFamList,', ' );
            
                   qliBUList.addAll(qlitBUset);
                   qliBUList.sort();
                   String bizUnit = string.join(qliBUList,', ' );
            if(quote.RollupofProductFamilies__c != productFamily && quote.BusinessUnit__c != bizUnit){
                 quote.RollupofProductFamilies__c = productFamily;
                 quote.ProductBusinessUnits__c = bizUnit;
                   quotesToUpdate.add(quote);
                   }
        }
        upsert quotesToUpdate;
             
        
        test.startTest();
    //    if(quotesToUpdate.size()>0 && listQLI.size()>0){
         
         QuoteRollupPFBU.updateQuote(listQLI);
  //      }
        test.stopTest();
       
    }
    
    


}


Trigger

trigger PrimaryQliTrigger on QuoteLineItem (before insert, before update, after insert, after update, before delete, after delete) {
    
        if(Trigger.isBefore){
        if(Trigger.isInsert){   
        }
        if(Trigger.isUpdate){
                    }
        if(Trigger.isDelete){
                    }
    }
    
 if(Trigger.isAfter){
        if(Trigger.isInsert){ 
             QuoteRollupPFBU.updateQuote(trigger.new);
        }
       if(Trigger.isUpdate || Trigger.isInsert ){
       //    QuoteRollupPFBU.updateQuote(trigger.new);
                    }
        if(Trigger.isDelete){
                    }
    }    


    
    

}